Well, with North Korea setting off something that might have been a nuclear device, it’s starting to show up in the darndest places. Everyone’s favorite millenial talk show host, Glenn Beck, not only mentioned it on his radio program this past Monday, but also put a link on the main page of his site for a couple of days. Then it got Farked. I suppose it’s only a matter of time now before it gets Slashdotted as well.

With the increased attention, some old criticisms have arisen, as well as some misunderstandings. For example, on Fark, someone said:

I thought it was funny how people are playing with this and think they were “safe” if they weren’t in the circle.

Here’s a mockup I did of the kind of blast damage you could expect from a single 1980’s era Russian ICBM carrying 10 MIRV warheads, each capable of 750KT yield.

Oh my yes. That’s something that the HYDEsim code can theoretically support, since every detonation point is an object and there’s no limit on the number of objects you can have, but I never managed to add this capability. That’s because trying to figure out the UI for placing the MIRV impact points broke my head, and when I considered how to set all that in the URI parameters (for direct linking), a tiny wisp of smoke curled out of my left ear. Still, one of these days I should probably at least add a “MIRV ring impact” option so the young’n’s can get an idea of what had us all scared back in the old days.

The interesting challenge is that a strategic nuclear strike of that variety is going to involve a whole bunch of optimum-altitude air bursts. HYDEsim takes the simpler—and also, in this darkened day and age, more realistic—approach of calculating the effects of a ground burst. The difference is in no sense trivial: a ground burst has a lot of energy, both thermal and radiological, absorbed by the ground (oddly enough!). On the other hand, its highest overpressure distances are actually greater.

This is because shock energy drops with distance, of course. An optimum-altitude air burst would be a mile or two above the ground, so the highest pressures would be directly beneath the explosion, and would be smaller than if the same weapon exploded on the ground. With an air burst there’s less ground and man-made clutter to attenuate the shock waves as they spread out, so the total area taking some degree of damage due to overpressure is actually greater. (There are also very complex interactions between the shock waves in the air and those reflected off the ground, but those are way beyond my ability to simulate in JavaScript.)

Also, direct thermal radiation is spread over a much greater area with an air burst than with a ground burst—again, there’s less stuff in the way. The amount of fallout depends on the “cleanliness” of the warhead, but for an air burst it can actually be expected to be less than a groundburst.

People also claim that radiological energy (X-rays, neutron radiation, gamma radiation, etc.) will be the deadliest factor of all. Actually, it’s just the opposite, unless you’re discussing something like a neutron bomb. The amount of harmful direct-effect radiation that comes directly from the explosion is far, far smaller than the thermal energy. And yes, I know thermal radiation is direct-effect, but there’s a large practical difference between heat and other forms of radiation.

Put another way, if you’re close enough to an exploding nuclear warhead that the amount of radiation emitted by the explosion would ordinarily kill you, the odds are overwhelmingly high that the amount of shock wave and thermal energy arriving at your position will ensure that there won’t be time for you to worry about the radiation effects. Or anything else, really.

Remember: I’m talking there about direct radiation, not the EMP or fallout. That’s a whole separate problem, and one HYDEsim doesn’t address, to the apparent disgust of another Farker:

The site is useless without fallout and thermal damage.

Well, I don’t know about useless, but it’s admittedly not as representative of the totality of nuclear-weapons damage as it might otherwise be. Of course, HYDEsim is not specifically about nuclear detonations, as I showed when I mapped the Hertfordshire oil refinery explosion and djsunkid mapped the Halifax explosion of 1917. But I certainly admit that the vast majority of explosions in the range the tool covers are going to be from nuclear weapons.

The problem with mapping fallout is that it’s kind of weather dependent, just for starters; just a few miles-per-hour difference in wind speed can drastically alter the fallout pattern, and the position of the jet stream plays a role too. Also, the amount of fallout is dependent on the kind of detonation—anyone who was paying attention during the Cold War will remember the difference between “dirty” and “clean” nuclear warheads. (For those of you who came late: to get a “dirty” warhead, you configure a device to reduce the explosive power but generate a lot more fallout.)

Thermal effects are something I should add, but it’s trickier than you might expect. There’s actually an area around the explosion where there are no fires, because the shock effects snuff them out. Beyond that, there’s a ring of fire (cue Johnny Cash). So it’s not nearly as simple as charting overpressure, which is itself not totally simple.

And then there’s there whole “how to combine thermal-effect and overpressure rings in a way that doesn’t become totally confusing” problem. Get ambitious, and then you have the “plus the show fallout plume without making everything a total muddle” follow-on problem. Ah well, life’s empty without a challenge, right?

Okay, so I went through all that and didn’t actually get to my point, which is this: I’ve been rather fascinated to see how the tool gets used. When it was first published, there was a very high percentage of the audience who just went, “Cooool!”. That’s still the case. It’s the same thing that draws eyes to a traffic accident; it’s horrible, but we still want to see.

However, I also got some pushback from conservative types: how dare I publish such a thing, when it could only be useful to terrorists?!?!? Rather than play to the audience and inform them that I simply hate freedom, I mentioned that it was desirable to have people like you and me better understand the threats we face. It’s not like the terrorists can’t figure this stuff out anyway.

Now I’ve seen a bunch of people from the same ideological camp use HYDEsim to mock the North Koreans’ test, which apparently misfired and only achieved a yield of about 0.5KT. Others have taken that figure and plotted it in American cities, giving some scale to the dimension of this particular threat. Still others have done that, but with the yield the North Koreans had attempted to reach (thought to be 4KT), or even with yields up to 50KT. In most cases, these last are shown in conjunction with commentary to the effect of “now do you understand why this is a problem?”.

This is why I do what I do, whether it’s write books or publish articles or speak at conferences or build tools or just post entries here: to help people learn more about their world, and to help them share what they know and think and believe with others. Sometimes that’s worth saying again, if only to remind myself.